The present invention concerns a method and a system for recognizing driving-dynamic states of a vehicle, in particular, signals, which indicate the variations of the tire pressures of tires of a vehicle being used for the purpose of recognizing critical driving-dynamic states.
So-called vehicle stability controllers are used in vehicles, and particularly in passenger cars, for the purpose of recognizing driving-dynamic states of the vehicle which can result in critical situations (skidding, oversteer and understeer, locking of the wheels, . . . ) in the driving operation of the vehicle and for the purpose of controlling individual components of the vehicle, which can influence the driving-dynamic state of the vehicle, in such a way that a critical driving-dynamic state is changed into a non-critical driving-dynamic state, i.e., the vehicle is stabilized. Examples of such vehicle stability controllers are anti-lock braking systems, electronic stability programs (ESP), anti-skid controllers, devices for limiting the engine torque and the engine rotational speed, and devices for chassis damping. In order to recognize a driving-dynamic state of the vehicle, vehicle stability controllers use various sensors to measure parameters of the vehicle which, immediately or following an evaluation, enable conclusions to be drawn on the driving-dynamic state of the vehicle. They measure, for example, the braking force acting on the individual wheels, the accelerator pedal position or the supply of fuel to the engine, the engine rotational speed, the engine torque, the rotational speed of the individual wheels, the acceleration or retardation of the vehicle in the driving direction and in directions across the latter, the loading of the vehicle, etc. In addition, external parameters which enable conclusions to be drawn on, for example, the weather conditions (temperature, rain, snow, . . . ) or the distance from other vehicles can also be measured for the purpose of better recognizing and better correcting, together with the vehicle parameters, critical driving-dynamic states of the vehicle. If a critical driving-dynamic state has been recognized, individual, or several, devices of the vehicle which can influence the driving state of the vehicle are controlled, in dependence on the measured parameters, in such a way that the critical driving-dynamic state is corrected, or the vehicle is stabilized, i.e., in such a way that the vehicle is brought out of the critical driving-dynamic state into a non-critical, stabilized driving-dynamic state. The devices which influence the driving state of the vehicle include, inter alia, devices for controlling the braking force of the individual wheels, the engine rotational speed, the engine torque and the fuel supply.
Since, in critical driving-dynamic states, the influence of vehicle stability controllers is exerted, to a substantial degree, automatically, i.e., without involvement of the vehicle driver, evaluation of the currently driving-dynamic state must be performed with extreme care. This necessitates the measurement and evaluation of a large number of parameters or of particularly indicative parameters which permit a description of the driving-dynamic state. Different sensors, some of complex construction, which are mounted at different locations in the vehicle are normally used for this purpose. Furthermore, additional sensors or devices are used to monitor the operation of the sensors for the vehicle stability controllers or their operation.
Consequently, conventional vehicle stability controllers, and vehicle stability systems comprising the same, are of a very complex construction and require a complex control system in order to assure faultless operation. In addition, the fitting, maintenance and repair of such vehicle stability controllers/systems is rendered difficult due to the large number of different components mounted at different locations in the vehicle.
To overcome these problems, it is an object of the present invention to provide a method, and a system, which recognizes the driving-dynamic, in particular, critical driving-dynamic states of a vehicle, the number of necessary sensors and the complexity of the arrangement/control of the latter being reduced. In addition, the number of necessary vehicle parameters to be measured for the recognition of a driving-dynamic state is to be reduced.
The invention is based on the phenomenon whereby the wheel loads of the individual wheels vary in dependence on driving-dynamic states, resulting in a dynamic variation of the wheel circumferences, more precisely, of the circumferences of the tires of the individual wheels. These tire circumferential variations result in a variation of the internal volume of the tires and, consequently, in a variation of the pressure in the individual tires. These pressure variations of the individual tires are measured and, according to the invention, compared and evaluated in order to draw conclusions on a driving-dynamic state of the vehicle and, in particular, to recognize a critical driving-dynamic state of the vehicle.
For this purpose, in the case of the method, according to the invention, for recognizing driving-dynamic states of a vehicle, respectively one reference pressure is isochronously measured for each of at least two tires of the vehicle. Respectively one current pressure is then isochronously measured for each of the at least two tires and compared, respectively, with the corresponding reference pressure for the purpose of determining a variation of the pressure of each of the at least two tires. The pressure variations of the at least two tires are then compared with each other. The determined pressure variations of the at least two tires and the result of the comparison of the pressure variations of the individual tires with each other are evaluated in order to generate vehicle information which indicates the driving-dynamic state of the vehicle and, in particular, enables conclusions to be drawn on whether the recognized driving-dynamic state is a critical driving-dynamic state.
The reference pressures of the at least two tires can be measured for a predefined driving-dynamic state and/or on a carriageway with a predefined surface quality.
An improved recognition of driving-dynamic states of the vehicle can be achieved if the isochronous measurement of the current pressures for the at least two tires is performed continuously, i.e., during the entire driving operation of the vehicle, or repeatedly at determined instants, the time interval of which is preferably varied in dependence on other vehicle parameters, or continuously during a predetermined interval of time, the length of which is preferably determined by other vehicle parameters, or repeatedly, at predetermined instants for a predetermined interval of time, other vehicle parameters preferably being taken into account in this case likewise.
In order to determine a temporal course of the pressure variations of an individual tire, at least two pressure variations of a tire occurring in temporal succession are compared.
Similarly, a temporal course of the pressure variations of the at least two tires can be determined by comparing with each other the pressure variations of the at least two tires for at least two pressure variations occurring in temporal succession.
The temporal course of the pressure variations of a tire can also be evaluated for at least one tire.
Likewise possible is an evaluation of at least two comparisons of the isochronously occurring pressure variations of the at least two tires for temporally successive instants at which isochronously occurring pressure variations were measured.
It is also preferable for the temporal course of the pressure variations of the at least two tires to be evaluated for at least two pressure variations occurring in temporal succession.
Using one or more of these evaluations of the pressure variations, it is possible to generate driving state information which better represents the driving-dynamic state of the vehicle.
Furthermore, provision is made for the generation of carriageway information which indicates the surface quality of the carriageway on which the vehicle is moving. According to the invention, the carriageway information is generated by comparison of the temporal course of the pressure variations of at least one of the at least two tires.
In addition, it is possible to generate the carriageway information by additionally evaluating the comparison of the temporal course of the pressure variations of the at least two tires with one another.
In order to stabilize the vehicle in dependence on its known driving-dynamic state, the driving state information and/or the carriageway information is used to control devices of the vehicle which stabilize the driving-dynamic state of the vehicle when a critical driving-dynamic state has been recognized.
In addition, the driving state information and/or the carriageway information can be used to control (calibrate, monitor, activate, deactivate, . . . ) further sensors which are mounted in the vehicle for the purpose of recognizing driving-dynamic parameters.
An object of the invention is also achieved by a system for recognizing driving-dynamic states of a vehicle, the system according to the invention being operated using the above-mentioned method according to the invention.
The invention provides a system which includes pressure sensors which are arranged for the purpose of measuring the pressure of at least two tires of the vehicle, and a processor unit which is connected to the pressure sensors and receives and evaluates signals from the pressure sensors which respectively indicate the pressures measured by the corresponding sensor, there being provided driving state signals, generated by the processor unit, which indicate a driving-dynamic state of the vehicle on the basis of the signals of the pressure sensors.
The system can also include at least one driving stability controller, connected to the processor unit, which serves to stabilize the driving-dynamic state of the vehicle and receives the driving state signals for this purpose.
In addition, it is possible to use a control unit which is connected between the processor unit and the at least one driving stability controller, and at least one driving state sensor which is connected to the control unit.
The control unit preferably generates control signals, for the at least one driving stability controller, which are based on the driving state signals and/or signals from the at lest one driving state sensor.
In order to generate driving state signals which better represent the driving-dynamic state of the vehicle, the processor unit is connected to the at least one driving state sensor in order to obtain signals from the at least one driving state sensor for generating the driving state signals.
Preferred embodiments of the invention are described in the following with reference to the appended figures.